Vacuum-tube device



March 3, 1931 INVENTOR Hubert M. Freeman ATTORNEY Patented Mar. 3, 1931 UNITED STATES PATENT ori-Ica HUBERT 1L FBEmAN, OF EAST PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTIIG- HOUSE ELECTRIC VANIA & MANUFACTURING COMPANY, A CORPORATION F .PENNSYL- vacUUn-TUBE nevica Application led November 7, 1922, Serial Io. 599,497. Renewed Iovcmber 27, 1989.

My-invention relates tovacuum-tube devices and more particularly'to the structure of such devices.V

The principal object of my invention is to 5 provide a vacuum-tube construction compris'- ing an equ'ipotential cathode element and an exciting element therefor, wherein the potential ofthe cathode element is substantially independent of the alternating currents supplied to the exciting element.

Another object of my invention is to provide a vacuum-tube construction of the class described, embodying a. design wherein the cathode element is connected directly to the grounded point of such circuits as are asociated therewithfthereby increasing the cihciency of operation of the tube by avoiding capacity effects between the cathode element and the other elements of the system and ground.

In the design and manufacture of detecting or amplifying vacuum tubes of the above-` mentioned class prior to my present invention, the usual practice has been'to connect the equipotential cathode element directly to one of the supply leads for the exciting element, within the evacuated portions of the tube. Such connection makes 'possible a l vacuum-tube construction wherein only four 3 terminalvpins are required.

In practice, it has been observed that when a single tube having theV above-mentioned in ternal cathode connection was employed, the usual so-called alternating-current hum was entirely absent in the operation of the tube. Howeven' when a number of such tubes were connected in cascade, .there appeared an appreciable alternating-current hum which was very troublesome.

After considerable experimental work, I have found that the above indicated diiiiculties are due to the fact that the alternatingcurrent supply circuit for the heater element imparts, tot-he equipotential cathode member, a varying potential which is represented' by the drop in potential in the portions of the heater supply circuit between the contacting surface of the terminal pin and the point of connection of the equ'potential cathode element to the supply circuit. l

Y The above-mentioned undesirable results are avoided in my invention by conn the lead from the equipotential cathode element directly to a point which is common to tube and to the heater supply circuit,-viz., to thecontacting surface on one of the heater supply-circuit terminal pins.

With these and other 'objects and applications in view, my invention further consists in the details of construction and arrangement hereinafter described and claimed and illustrated in the accompanying drawing, wherein:

Figure l is a perspective view of a vacuumtube device embodying my invention together with suitable operatingA circuit connections, a portion of the vacuum-tube containing walls being broken away and the plate and grid elements being shown partly in longitudinal section,

Fig. 2 is an enlarged detail longitudinal sectional view of the cathode construction shown in Fig. l, and

Fig. 3 is a diagrammatic view of circuits and apparatus embodying my invention.

In the form of embodiment of my invention shown in the drawing, I provide an elongated tubular container 1 having a re-entrant portion 2 terminating in a supporting press 3.

A cathode construction 4 comprises a mass of refractory material 5 in the form of an elongated solid cylinder having a pair of adjacently positioned perforations 6 and 7 extending longitudinally therethrough. The perforations 6 and 7 are of such dimensions as to receive a tilamentary element 8 which is inserted up through Aone perforation and down through the other to provide a iilament of substantially inverted U shape, comprising parallelly extending portions 9 and 11 and a bent portion 12.

The distance between the parallel portions 9 and 11 of the filament 8 is so small that the magnetic ield established by currents traversing one portion or section substantially neutralizes the magnetic field established by currents traversing the other section, thereby minimizing the effect of` the alternating supply currents upon the operation of the vacu- -the input and output circuits of the vacuum-:

or With other substances which, when sub- 11m-tube device. The filament 8 may be energized by connecting `the same to the two hl- Ya-nient supply conductorsvl and 14 which are supported in the press 3 and "which are provided with external extensions 15 and 16,V respectively.

The cylindrical member 5 is preferably made of some insulating refractory material which, When heated to the temperature of the heater element 8, is free from chemical action therewith. In the course of much experimental Work, I have lfound that Zircon in combination with a binding material, as clay', possesses such desirable characteristics.

A member 17, which forms the equipoten tial cathode surface, is shown in-the form of a tube having its inner surface rigidly embracing the tubular insulating member 5. The outer surface of the member 17 may be coated with oxides of barium and strontium jected to heat, are rendered thermionieally active.

The cathode construction may be supported by means lof a carrier rod 18 rextending from the press 3 and secured thereto as hereinafter described. In practice. it has desirable to provide a spring connection between the cathode construction 4 and the supporting carrier rod 18 in order to provide for theexpansion and the contraction of the heating element 8. The desired resilient mounting for the cathode construction 4 may be obtained by Welding a strip 19 to the upper end of the cathode construction, preferably to the. tubular member 17, and by interconnecting the strip 19 and the carrier rod 18 by means of a resilient member 21. The strip 19 is insulatingly spaced from the heater element 8 to prevent the carrier rod 18 being impressed with varying potentials from the heater element 8. The carrier rod 18 may be extended through the press to provide an external connection 22 for the equipotential cathode member 17.

The cathode construction 4 may be surrounded by plate and grid elements 23 and 24 of conventional design. By wayof illustration, the grid 24 is shown helical in shape with its longitudinal aXis co-inciding with that of the heater element 8. The grid 24 is supported in position by means of a carrier rod 25 extending from the press 3 and welded to the several helices of the grid to impart additional stiifness to the grid eonstruction.

The cylindrical plate 23 is symmetrically positioned with respect to the previously mentioned elements and is supported by carrier rods 26 and 27 which are mounted in the press 3, one of the carrier rods, say 27, being extended through thepress 3 to provide an external circuit terminal 28.

The envelope 1 may be provided with a base 29 which comprises `a circular insulatbeen foundV ing member 31 and a collar 31(1,opposite ends of the latter rigidly embracing the re-entrant tube 2 and the insulating member 3l in any approved manner. he lovver end of the insulating block 31 may be provided with a plurality of hollow terminal pins 32 and 33, 34 and 35.` The several external connections 15, 1G, and 28 are disposed in the hollow portions of the terminal pins in such 'manner that terminal pins 32 and 33 are connected to the heater element 8 and the pins 35 and 34 are connected to the plate and 'grid element-s. respectively. perforation 3G, which extends through the insulating block 31, may be positioned immediately1 adjacent to the terminal pin 33 for reasons which will appear hereinafter. f

As pointed out in the foregoing portions of the specification, it is desirable that the equipotential cathode member 17 be connected to the heater. supply circuit at a point which is common Ato the input and the output circuits of the vacuum tube and to the heater supply circuit. Such desired result is obtained by extending the external connection 22 from the equipotential cathode member 17 through the perforation 36 in the insulating block 3.1 and securing said connection to the contacting surface of one of the heater Vsupply terminal pins. say 33. Such construction avoids any possibility ofthe occurrence of a variable potential on the equipotential cathode member 17 asa result of impedance drops in the heater supply conductors Within the tube.

Then-the tube above described is inserted in a socket having connect-ionsto the circuit described in detail in connectionwith Fig. 3, the socket connections will be as-indicat'ed at the bottom ofFig. 1. The reference numerals indicating the circuit element in Fig. 1,

have the meaning stated for the same numerals in Fig. 3.

Fig. 3 is a diagrammatic vieu7 of a vacuumtube construction embodying my invention, together with circuit connections whereby the tube may function as an amplifier of :ilterto the equipotential cathode element 17 andl includes a. detecting device 41 and a source 42 of direct-current energy. The inputcircuit formed by the conductors 37 and-38 and the outgoing circuit 39 are interconnected at. a

commonjunction point 43. A source o f alter nating-current energy (not shown) of commercial frequency is operatively connected to the heater element 8 through a transformer 44. The supply circuit of the heater element .8 is connected to the junction point 43 'of the input and output circuits to' form a common junction point for the three circuits which corresponds to the contacting surface of the terminal pin 33. The cathodev structure 4 may be connected to ground by means of the ground conductor 45 extending from the common junction point 43 of the several circuits.

While I have shown a single embodiment of my invention, for the purpose of describing the same and illustrating the construction and operation thereof, it is apparent that various changes and modifications may be made therein without departing from the spirit of my invention. I desire, therefore,

that only such limitations shall be'imposed thereon as are indicated by the appended claims or demanded by the prior art.

I claim as my invention: 1. The combination with a tube having an equipotential cathode member and a separate heater element, of a base for said tube cary.

ing a pair of terminal ins for said heater element, said membery ing directly connected to one of said terminal pins.

2. A space-current device comprising a tube having an equipotential cathode member and a heater element, a base for said tube comprising an insulating member, a pair of terminal pins having contact surfaces carried by said insulating member, and'means connecting said terminal pins to said heater element and means connecting said cathode member to the con`tacting surface of one of said ins.

3. combination, a space-current device comprising an anode element, acathode element, a controlling element and energizing means for said cathode element, mtercon'- nected input and output circuits for said elei `and means for grounding said junction ments having a single junction point, an exciting circuit for sald energizing means, said exciting circuit being connected to said firstmentioned circuits at said junction point, and means for grounding said junction point.

4. In combination, a space-current device comprising an anode element, a controlling element, a cathode element and energizing means for said cathode element, said energizing means comprising a looped filament, interconnected input uand output circuits for `said elements havinga singlejjunction point,

an exciting circuit for said energiz means, said exciting circuit being connect to said first-'mentioned circuits at said unction point, int. 5. In combination, a space-current evi comprising an anode element, a controlling element, a cathode element and energizing means for said cathode element, said energizing means comprising a V-shaped filament, interconnectedinput and output circuits for said elements ,having a single junction point, an exciting circuit for said energizing means, said exciting circuit being connected to said first-mentioned circuits at said 'unction point, and means for grounding said junction oint. 6. In combination, a space-current device an anode element, a control elecomprising1 ode element and energizing means ment, a cat for said cathode element, said energizing nectedto said anode element and said cathode element whereby said circuits have a common junction point, an exciting circuit for said energizing means, said exciting circuit being connected to said first-mentioned circuits at said junction point, said lament having one leg thereof directly connected to said junction point, and means for grounding said .junctlon point. 7. In combination, a space-current discharge device comprising an anode element, a control element, a cathode element and energizing means for said cathode element, an lnput circuit connected to said control element and said cathode element, an output circuit connected to said anode element and said cathode element `whereby Ysaid circuits have a common junction point, an exciting circuit for said energizing means, said exciting circuit being connected to saidrst mentioned circuits at said junction point. 8. In combination, a space-current dis- 'charge device comprising an anode element, a control element, a cathode element and energizing means for said cathode element, an input circuit connected to said control element'and said cathode element, an output circuit connected to said anode element and Cathode member and a separate heater element, terminal members for said heater element, and a direct electrical connection between said cathode member and oneof said terminal members.

' 10. In a tube having van equipotential cathode member and a separate heater element, terminal members forsaid heater element, and means for mainta' said cathode member and one .of said terminal members at the same potential:v i c '11. An" lectron-discharge device comprisin an evacuated` vessel, an equipotential cat ode member and a separate heater ele@ ment therefor positioned 1ns`ide said vessel, terminal members for said heater element sitined outsideisaid vessel, and means or maintaining `said cathode member andone of said terminal members at the same potential.

In testimony whereof, I have hereunto subscribed my name this 27th day of October,

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